1. Field of the Invention
The present invention relates to high-precision position, navigation and/or timing (PNT) solutions based on signals received from overhead assets such as satellites and, in particular, to techniques suitable for providing rapid acquisition access to such PNT solutions without resort to a generally proximate, terrestrial ground station with fixed and precisely known position.
2. Description of the Related Art
Traditional precision satellite navigation techniques such as real time kinematic (RTK) and differential GPS (DGPS) techniques commonly used in surveying and high accuracy timing applications, depend on a terrestrial reference station in close proximity to the receiver to provide the receiver with measurements from satellites within view of both the terrestrial reference station and the receiver itself. The receiver commonly differences these reference station measurements (typically carrier phase measurements) with its own, and extracts extremely accurate and precise positioning and timing information from the differenced measurements. GPS-based precise point positioning (PPP) techniques employ a network of terrestrial reference stations to observe satellite orbits and, based thereon, broadcast corrections to receiver equipment via geosynchronous (GEO) satellites or a terrestrial communications network. In each case, centimeter-level in positioning solutions may be achieved. Unfortunately, RTK, DGPS and PPP techniques all require warm-up (convergence) times of about thirty (30) minutes to achieve high accuracy and/or integrity solutions. In addition, requirements for fixed terrestrial reference stations and/or coverage patterns of terrestrially-based, or geosynchronous overhead, correction distribution infrastructure can limit availability of conventional high-precision navigation techniques.
Improved techniques are desired.